Question

80 bulbs are selected at random from a lot and their life time (in hrs) is recorded in the form of a frequency table given below :

Life time (in hours)	300	500	700	900	1100
Frequency	10	12	23	25	10

The probability that bulbs selected randomly from the lot has life less than 900 hours is:

Options

• `11/40`

• `5/16`

• `7/16`

• `9/16`

Answer 1

`bb(9/16)`

Explanation:

Total number of bulbs in a lot, n(S) = 80

Number of bulbs whose life time is less than 900 h, n(E) = 10 + 12 + 23 = 45

Probability that bulbs has life time less than 900 h = `(n(E))/(n(S)) = 45/80 = 9/16`

Hence, the probability that bulb has life time less than 900 is `9/16`.